Question

Classify each of these sea creatures as plankton, nekton, or benthos: shrimps, dolphins, sea stars, krill, coral, manatees, and algae.

Short answer

Shrimps: Benthos, Dolphins: Nekton, Sea Stars: Benthos, Krill: Plankton, Coral: Benthos, Manatees: Nekton, Algae: Plankton.

Step-by-step solution

Understanding Ecosystem Categories

Before classifying the sea creatures, it's important to understand what plankton, nekton, and benthos are. Plankton are organisms that float in the water and are typically moved by tides and currents. Nekton are active swimmers like fish and marine mammals. Benthos live on or near the sea floor, such as crabs and sea stars.

Classifying Shrimps

Shrimps often live close to the ocean floor and are mainly crawling or walking. Thus, they are classified as benthos.

Classifying Dolphins

Dolphins are known for their swimming abilities and spend their life actively swimming in the ocean. They are classified as nekton.

Classifying Sea Stars

Sea stars typically reside on the ocean floor and are not capable of swimming or floating. They are part of the benthos category.

Classifying Krill

Krill, while tiny, swim weakly and are mostly moved by ocean currents. Thus, they fall under the plankton category.

Classifying Coral

Coral live fixed on the ocean floor and do not move, classifying them as benthos.

Classifying Manatees

Manatees swim actively in the water like dolphins, so they are classified as nekton.

Classifying Algae

Algae, often floating in the water and moved by currents, are considered plankton.

Key concepts

Plankton

Plankton are fascinating and diverse organisms that are crucial to aquatic ecosystems. These tiny drifters can be found floating in the ocean, propelled by the tides and currents rather than their own movement. Plankton is divided into two main categories: phytoplankton and zooplankton.

**Phytoplankton** are like the plants of the ocean. They generate around 50% of the world's oxygen thanks to photosynthesis. They also form the base of most aquatic food webs, providing nourishment for a wide range of marine life. Examples include diatoms and some types of algae.

**Zooplankton**, on the other hand, are like the tiny animals of the plankton world. They feed on phytoplankton and are a vital food source for larger marine creatures. Krill, which are classified as zooplankton, are a perfect example. They are small crustaceans that drift in the water and are essential in the diet of many marine species, including whales.

• Plankton are moved primarily by water currents.
• They play a key role in oxygen production and the marine food chain.
• Phytoplankton are plant-like, while zooplankton act more like animals.

Nekton

Nekton are the active swimmers of the aquatic world. They differ from plankton in that they can control their movements and swim against the current. This group includes a wide variety of animals, from fish to marine mammals like dolphins and manatees.

These creatures are known for their ability to travel and explore different areas of the ocean. Nekton are mostly vertebrates, which means they have a backbone, but some invertebrates like squid also fall under this category. They are key players in the marine ecosystem because they help connect different ecological zones by moving nutrients and energy around.

• Nekton are strong swimmers and can move against currents.
• They include a diverse group of animals, mostly vertebrates like fish and dolphins.
• Nekton are crucial for nutrient and energy distribution in marine environments.

Benthos

Benthos are the dwellers of the ocean floor. Unlike plankton and nekton, these organisms are either stationary or move near the bottom of bodies of water. Benthos include creatures such as sea stars, crabs, and coral.

Benthic organisms play an essential role in the aquatic ecosystem because they contribute to the recycling of nutrients by breaking down dead matter. They come in two types: *epifauna*, which live on top of the seabed, and *infauna*, which live buried within the seafloor sediment.

Certain benthic organisms, like coral, are integral to forming marine habitats. Coral reefs, for instance, provide shelter and breeding grounds for many marine species.

• Benthic creatures are found on the ocean floor.
• They include both mobile and stationary organisms, like crabs and coral.
• Benthos contribute to nutrient cycling and habitat formation.